Characterization of the polyphenol composition of 20 cultivars of cider, processing, and dessert apples (Malus × domestica Borkh.) grown in Virginia

Identification and Mining of Functional Components of Polyphenols in Fruits of Malus Germplasm Resources Based on Multivariate Analysis

Polyphenols are important functional components that have anti-cancer and anti-inflammatory effects. Apple fruit is rich in polyphenols and is one of the dietary sources of polyphenols. The polyphenol components and contents of the peel and pulp of 74 Malus sieversii (Led.) Roem. and 26 Chinese Malus germplasm resources were determined using ultra-high-phase chromatography (UPLC) and liquid chromatography-mass spectrometry (LC-MS). The results showed that 34 components were detected in the peel and 30 in the flesh, and that the polyphenol components and contents of the different germplasm resources were significantly different; the polyphenol content of Malus sieversii (Led.) Roem. was significantly higher than that of the other local varieties, and the polyphenol content in the peel was also higher than that in the flesh. Rutin, quercetin 3-O-arabopyranoside, kaempferol 3-O-rutinoside, and peonidin 3-O-galactoside were detected only in the peel. The total polyphenol content in the peel ranged from 949.76 to 5840.06 mg/kg, and the polyphenol content in the pulp ranged from 367.31 to 5123.10 mg/kg. The cluster analysis of polyphenol components and contents in peel and pulp showed that 100 Malus germplasm resources could be grouped into four categories. Principal component analysis of 34 kinds and 30 kinds of polyphenols in peel and pulp of 100 resources was performed. If the eigenvalue is greater than 1, eight and seven principal components are extracted, respectively. Five Malus resources with high polyphenol content in the peel and pulp were selected: 'XY-77' (peel: 5840.06 mg/kg, pulp: 5123.10 mg/kg; 'LF-09' (peel: 4692.63 mg/kg, pulp: 3729.79 mg/kg); '2012-5' (peel: 4377.61 mg/kg, pulp: 3847.54 mg/kg); '29028' (peel: 5088.05 mg/kg, pulp: 3994.61 mg/kg); and '11-01' (peel: 5154.45 mg/kg, pulp: 3616.15 mg/kg). These results provide us with information regarding the polyphenol composition and content of the wild apple resources and local cultivars. The high polyphenol content resources obtained by screening can be used as raw materials for the extraction of polyphenol components and functional fruit juice processing and can also be used as parents for functional fruit creation and variety breeding.

Polyphenolic profile, processing impact, and bioaccessibility of apple fermented products

Health-promoting foods have become increasingly popular due to intensified consumer interest and awareness of illnesses. There is a global market for apple fruits, which are affordable, nutritious, tasty, and produced in large quantities for direct consumption as well as food processing to make derived products. The food matrix of apples is suitable for fermentation, besides containing a high amount of phenolics and polyphenols. Fermentation of apples is one of the most common methods of preserving apple fruit and its byproducts. With different fermentation techniques, apple fruit can be used to make a wide range of products, such as fermented apple juice, cider, liqueurs, apple cider, apple vinegar and fermented apple solids, because it is not only a low-cost and simple method of processing the fruit, but it can also sometimes increase the bioavailability of nutrients and the levels of components that can improve health and sensory quality. To understand the health benefits of food products and how the fermentation process impacts polyphenols, it is also crucial to observe the effects of digestion on polyphenol bioaccessibility. Polyphenolic profile changes can be observed via both in vitro and in vivo digestion methods; however, in vitro digestion methods have the advantage of observing every step of gastrointestinal track effects and have less cost as well. In this review, the polyphenolic profile, processing impact, and bioaccessibility of apple-fermented products is assessed, with most available studies showing polyphenol profiles and bioaccessibility in apple varieties and fermented apple products.

Chemical Characterization, Sensory Definition and Prediction Model of the Cider Dryness from New York State Apples

Cider is a fermented drink obtained from apple juice. As a function of the used apple cultivar, cider can be classified in four different categories (dry, semi-dry, semi-sweet, sweet), distinguished by the attribute of "dryness," which reflects the sweetness and softness perceived. The dryness level is defined by scales (IRF, NYCA scales) based on the residual sugar, titratable acidity and tannin contents. Despite some adjustments, these scales show limitations in the prediction of actual perceived dryness, as they cannot consider the complicated interrelation between combined chemical compounds and sensory perception. After defining the perceived sensory dryness and its sensory description by using the quantitative descriptive analysis (QDA) method, a multivariate approach (PLS) was applied to define a predictive model for the dryness and to identify the chemical compounds with which it was correlated. Three models were developed, based on three different sets of chemical parameters, to provide a method that is easily applicable in the ordinary production process of cider. The comparison between the predicted rating and the relative scales scores showed that the models were able to predict the dryness rating in a more effective way. The multivariate approach was found to be the most suitable to study the relation between chemical and sensory data.

Safety Assessment of Apple-Derived Ingredients as Used in Cosmetics

The Expert Panel for Cosmetic Ingredient Safety (Panel) reviewed the safety of 26 apple-derived ingredients, which reportedly function mostly as skin conditioning agents in cosmetic products. Because apple-derived ingredients may be obtained from different apple cultivars, the composition of ingredients derived from different cultivars should be similar to that of ingredients reviewed in this safety assessment. Additionally, industry should continue to use good manufacturing practices to limit impurities that could be present in botanical ingredients. The Panel reviewed the available data to determine the safety of these ingredients and concluded that 21 of these ingredients are safe in cosmetics in the present practices of use and concentrations described in this safety assessment. However, the Panel also determined that the available data are insufficient to determine the safety of Pyrus Malus (Apple) Root Extract, Pyrus Malus (or Malus Domestica) (Apple) Stem Extract, Malus Domestica (Apple) Callus Extract, and Malus Domestica (Apple) Oil.

A Preliminary Study of Yeast Strain Influence on Chemical and Sensory Characteristics of Apple Cider

During the fermentation of apple juice, yeast metabolism creates complex biosynthetic pathways which produce a range of compounds responsible for the organoleptic qualities of cider. In this study, basic cider quality parameters were measured to investigate the influence of six yeast strains on cider made from three apple varieties (‘Pink Lady’, ‘Sturmer’, and ‘Bulmer’s Norman’). Measurement of pH, titratable acidity, and total phenolic content revealed that yeast can influence cider attributes, albeit variety and season dependent. Descriptive sensory analysis using a trained sensory panel was conducted on cider made from ‘Pink Lady’ apples and the same six yeast strains. The sensory panel significantly differentiated the yeast strains on the attributes of ‘fresh apple’, ‘earthy’ and ‘pear’. Identifying the variety specific influence of individual yeast strains on chemical and sensory characteristics of apple cider will provide cider makers with an enhanced understanding when choosing yeast strains.

Purification and Characterization of a Dark Red Skin Related Dimeric Polyphenol Oxidase from Huaniu Apples

The distinct dark-red skin of Huaniu apples renders them attractive to customers. However, the mechanism that leads to the development of the color of the fruit is unclear. In this study, we found that compared with red Fuji (a bright-red apple cultivar), Huaniu apples had higher contents of (−)-epicatechin (EC), (−)-epigallocatechin (EGC), (−)-gallocatechin gallate (GCG), and procyanidins (PCs) B2 and C1 in the peel, which implies that the polymerization of the flavanols and PCs may be correlated with the dark-red skin of the fruit. Using EC as a substrate, we purified an enzyme from Huaniu peel. We performed protein sequencing and discovered that the enzyme was a polyphenol oxidase (PPO). The molecular weight of the enzyme was approximately 140 kDa, which we estimated by native-PAGE and SDS-PAGE, while it was 61 kDa by urea-SDS-PAGE, from which we discovered that the PPO was a dimer. We observed the lowest K_m value for catechol (0.60 mM), and the best substrate was 4-methylcatechol, with a V_max of 526.32 U mg⁻¹ protein. EC is a suitable natural substrate, with a K_m value of 1.17 mM, and 55.27% of the V_max/K_m of 4-methylcatechol. When we used EC as a substrate, the optimum temperature and pH of the PPO were 25 °C and 5.0, respectively. In summary, we purified a dimeric PPO from Huaniu apples that showed high activity to EC, which might catalyze the polymerization of flavanols and PCs and lead to the dark-red color development of the fruit.

More than a Virulence Factor: Patulin Is a Non-Host-Specific Toxin that Inhibits Postharvest Phytopathogens and Requires Efflux for Penicillium Tolerance

Mycotoxin contamination is a leading cause of food spoilage and waste on a global scale. Patulin, a mycotoxin produced by Penicillium spp. during postharvest pome fruit decay, causes acute and chronic effects in humans, withstands pasteurization, and is not eliminated by fermentation. While much is known about the impact of patulin on human health, there are significant knowledge gaps concerning the effect of patulin during postharvest fruit-pathogen interactions. Application of patulin on six apple cultivars reproduced some blue mold symptoms that were cultivar-independent and dose-dependent. Identical symptoms were also observed in pear and mandarin orange. Six Penicillium isolates exposed to exogenous patulin exhibited delayed germination after 24 h, yet all produced viable colonies in 7 days. However, four common postharvest phytopathogenic fungi were completely inhibited by patulin during conidial germination and growth, suggesting the toxin is important for Penicillium to dominate the postharvest niche. Using clorgyline, a broad-spectrum efflux pump inhibitor, we demonstrated that efflux plays a role in Penicillium auto-resistance to patulin during conidial germination. The work presented here contributes new knowledge of patulin auto-resistance, its mode of action, and inhibitory role in fungal-fungal interactions. Our findings provide a solid foundation to develop toxin and decay mitigation approaches.

The Use of Temporal Check-All-That-Apply and Category Scaling by Experienced Panellists to Evaluate Sweet and Dry Ciders

Cider is a growing market in North America, but more studies need to be completed to fully understand ciders’ sensory properties. The primary objective of this study was to identify the differences in the sensory properties of ciders described as “sweet” or “dry” using both static (category scales) and dynamic (temporal check-all-that-apply, TCATA) sensory methodologies. The secondary objective was to evaluate experienced panellists with a familiar methodology (category scales) and an unfamiliar methodology (TCATA). The sweet ciders were characterized by sweet, floral, cooked apple, and fresh apple attributes, and they had a sour aftertaste. The dry ciders were found to be bitter, sour, earthy, and mouldy, and they had a sour and bitter aftertaste. The experienced panellists produced reproducible results using both methodologies; however, they did not find small differences between the cider samples. Future research should investigate a wider range of cider and investigate ciders’ aftertaste. More studies need to be completed on experienced panellists and on when researchers and the food industry should use them.

Synthesis of Biobased Phloretin Analogues: An Access to Antioxidant and Anti-Tyrosinase Compounds for Cosmetic Applications

The current cosmetic and nutraceutical markets are characterized by a strong consumer demand for a return to natural products that are less harmful to both the consumers and the environment than current petrosourced products. Phloretin, a natural dihydrochalcone (DHC) found in apple, has been widely studied for many years and identified as a strong antioxidant and anti-tyrosinase ingredient for cosmetic formulations. Its low concentration in apples does not allow it to be obtained by direct extraction from biomass in large quantities to meet market volumes and prices. Moreover, its remarkable structure prevents its synthesis through a green process. To overcome these issues, the synthesis of phloretin analogs appears as an alternative to access valuable compounds that are potentially more active than phloretin itself. Under such considerations, 12 chalcones (CHs) and 12 dihydrochalcones (DHCs) were synthesized through a green Claisen-Schmidt condensation using bio-based reagents. In order to evaluate the potential of these molecules, radical scavenging DPPH and anti-tyrosinase tests have been conducted. Moreover, the UV filtering properties and the stability of these analogs towards UV-radiations have been evaluated. Some molecules showed competitive antioxidant and anti-tyrosinase activities regarding phloretin. Two compounds in particular showed EC₅₀ lower than phloretin, one chalcone and one dihydrochalcone.

A Comparison of Laboratory Analysis Methods for Total Phenolic Content of Cider

Total phenolic content is widely accepted as a key measure of quality for cider. Apple juice and cider, made from six apple varieties including dessert and cider apples, were analysed for total phenolics using three different methods: (a) the Folin-Ciocalteu method, (b) the Somers method (a spectrophotometric method developed specifically for wine), and (c) ultra-performance liquid chromatography (UPLC) as a benchmark test. Of these approaches, the Somers method had the strongest correlation with UPLC with an R2 value of 0.99, whilst the Folin-Ciocalteu correlated with UPLC with an R2 value of 0.89. The Folin-Ciocalteu method also had a strong positive correlation with the Somers approach with an R2 value of 0.91. Correlations between methods were strongest for apple varieties that were naturally high in phenolic content. These results highlight the potential of the Somers method to rapidly, inexpensively, and accurately report the total phenolic content of apple juice and ciders made from dessert and cider apple varieties.

Monitoring Cider Aroma Development throughout the Fermentation Process by Headspace Solid Phase Microextraction (HS-SPME) Gas Chromatography–Mass Spectrometry (GC-MS) Analysis

Volatile organic compounds (VOCs) play a crucial role in cider quality. Many variables involved in the fermentation process contribute to cider fragrance, but their relative impact on the finished odor remains ambiguous, because there is little consensus on the most efficient method for cider volatile analysis. Herein, we have optimized and applied a headspace solid phase microextraction gas chromatography–mass spectrometry (HS-SPME GC-MS) method for the chemical analysis of cider VOCs. We determined that the 30 min exposure of a divinylbenzene/carboxen/polydimethylsiloxane (DVB/CAR/PDMS) solid phase microextraction (SPME) fiber at 40 °C yielded detection of the widest variety of VOCs at an extraction efficiency >49% higher than comparable fibers. As a proof-of-concept experiment, we utilized this method to profile cider aroma development throughout the fermentation process for the first time. The results yielded a very practical outcome for cider makers: a pre-screening method for determining cider quality through the detection of off-flavors early in the fermentation process. The aroma profile was found to be well established 72 h after fermentation commenced, with major esters varying by 18.6% ± 4.1% thereafter and higher alcohols varying by just 12.3% ± 2.6%. Lastly, we analyzed four mature ciders that were identically prepared, save for the yeast strain. Twenty-seven key VOCs were identified, off-flavors (4-ethylphenol and 4-ethyl-2-methoxyphenol) were detected, and odorants were quantified at desirable concentrations when compared to perception thresholds. VOCs varied considerably following fermentation with four novel strains of S. cerevisiae, evidencing the central importance of yeast strain to the finished cider aroma.

Volatile Profile of Mead Fermenting Blossom Honey and Honeydew Honey with or without Ribes nigrum

Mead is a not very diffused alcoholic beverage and is obtained by fermentation of honey and water. Despite its very long tradition, little information is available on the relation between the ingredient used during fermentation and the aromatic characteristics of the fermented beverage outcome. In order to provide further information, multi-floral blossom honey and a forest honeydew honey with and without the addition of black currant during fermentation were used to prepare four different honey wines to be compared for their volatile organic compound content. Fermentation was monitored, and the total phenolic content (Folin–Ciocalteu), volatile organic compounds (HS-SPME-GC-MS), together with a sensory evaluation on the overall quality (44 nontrained panelists) were measured for all products at the end of fermentation. A higher total phenolic content resulted in honeydew honey meads, as well as the correspondent honey wine prepared with black currant. A total of 46 volatile organic compounds for pre-fermentation samples and 62 for post-fermentation samples were identified belonging to higher alcohols, organic acids, esters, and terpenes. The sensory analysis showed that the difference in meads made from blossom honey and honeydew honey was perceptible by the panelists with a general greater appreciation for the traditional blossom honey mead. These results demonstrated the influences of different components in meads, in particular, the influence of honey quality. However, further studies are needed to establish the relationship between the chemical profile and mead flavor perception.

The Influence of Yeast Strain, β-Cyclodextrin, and Storage Time on Concentrations of Phytochemical Components, Sensory Attributes, and Antioxidative Activity of Novel Red Apple Ciders

The yeast strain and storage time is an important factor affecting the development of phytochemicals and sensory attributes in ciders. Therefore, the aim of this study was to determine the influence of yeast strains (Saccharomyces bayanus and Saccharomyces cerevisiae), β-cyclodextrin (BCD), and storage time on physicochemical parameters, contents of phenolic compounds (ultra-performance liquid chromatography with photodiode array detector coupled to quadrupole time-of-flight tandem mass spectrometry (UPLC–PDA–QToF-MS/MS)), antioxidative activity (free radical-scavenging ability (ABTS) and ferric reducing antioxidative power (FRAP) assay), and sensory attributes of new cider from the “Bella Marii” cultivar of red apple. The pH value, acidity, concentrations of alcohol, organic acids, and polyphenols; and the color and antioxidative properties were evaluated in red apple ciders immediately after fermentation and after three months of storage at 4 °C. S. cerevisiae SIHAFERM Finesse Red with BCD and SIHAFERM Finesse Red yeast strain especially contributed to obtaining ciders with a high content of the tested compounds. The use of BCD during fermentation significantly influenced the protection of bioactive compounds, by as much as 18%. Storage time had an impact on concentrations of the tested components (mainly on the total flavan-3-ols and phenolic acids). Based on the achieved values of parameters analyzed in red apple ciders and results of the consumer acceptance test, it may be concluded that red apple offers vast potential for the production of ciders with a high content of polyphenolic compounds.

Resource allocation trade-offs and the loss of chemical defences during apple domestication

BACKGROUND AND AIMS

Most crops have been dramatically altered from their wild ancestors with the primary goal of increasing harvestable yield. A long-held hypothesis is that increased allocation to yield has reduced plant investment in defence and resulted in crops that are highly susceptible to pests. However, clear demonstrations of these trade-offs have been elusive due to the many selective pressures that occur concurrently during crop domestication.

METHODS

To provide a robust test of whether increased allocation to yield can alter plant investment in defence, this study examined fruit chemical defence traits and herbivore resistance across 52 wild and 56 domesticated genotypes of apples that vary >26-fold in fruit size. Ninety-six phenolic metabolites were quantified in apple skin, pulp and seeds, and resistance to the codling moth was assessed with a series of bioassays.

KEY RESULTS

The results show that wild apples have higher total phenolic concentrations and a higher diversity of metabolites than domesticated apples in skin, pulp and seeds. A negative phenotypic relationship between fruit size and phenolics indicates that this pattern is driven in part by allocation-based trade-offs between yield and defence. There were no clear differences in codling moth performance between wild and domesticated apples and no overall effects of total phenolic concentration on codling moth performance, but the results did show that codling moth resistance was increased in apples with higher phenolic diversity. The concentrations of a few individual compounds (primarily flavan-3-ols) also correlated with increased resistance, primarily driven by a reduction in pupal mass of female moths.

CONCLUSIONS

The negative phenotypic relationship between fruit size and phenolic content, observed across a large number of wild and domesticated genotypes, supports the hypothesis of yield-defence trade-offs in crops. However, the limited effects of phenolics on codling moth highlight the complexity of consequences that domestication has for plant-herbivore interactions. Continued studies of crop domestication can further our understanding of the multiple trade-offs involved in plant defence, while simultaneously leading to novel discoveries that can improve the sustainability of crop production.

Juice Clarification with Pectinase Reduces Yeast Assimilable Nitrogen in Apple Juice without Affecting the Polyphenol Composition in Cider

The term "cider" refers to the fermented beverage produced from apples. The rapid growth in the cider industry coupled with the prominence of traditional, or craft, approaches emphasizes the need for research on cider production. A common problem in ciders is the production of sulfur off-aromas by yeast during fermentation. Prefermentation juice clarification has the potential to reduce the occurrence of unwanted sulfur off-aromas. Concerns that prefermentation juice clarification will reduce the yeast assimilable nitrogen (YAN) and polyphenols in the juice have limited the application of this practice by cider makers. In this study, 3 clarification methods were applied to 'York' apple juice, that is, static settling, centrifugation, and pectinase. Raw (control) and clarified juice were fermented to cider, and the impact of clarification on the physicochemical parameters, amino acids and polyphenol content of the juice and cider was assessed. Juice clarification by pectinase decreased YAN by 50%, while static settling and centrifugation increased the concentration of most amino acids by 83%. All clarification treatments lowered the concentration of total polyphenols in the juice (from 60% to 30%, P < 0.05) and affected the individual polyphenols in the juice but these changes were not evident in the ciders. These findings demonstrate that prefermentation juice clarification results in changes in the chemistry profiles of apple juice. These changes were however not evident in the ciders. This approach therefore has the potential to limit the production of sulfur off-aromas during cider production without adverse effects on quality. PRACTICAL APPLICATION: Clarification of apple juice changes polyphenol and nitrogen contents, factors known to affect cider quality. However, these differences in the chemical profile of apple juice may not be reflected in the finished ciders. These findings demonstrate that juice clarification can be employed in cider making without affecting the quality. Cider makers should not assume that changes in apple juice imparted by clarification will be reflected in the finished ciders. Outcomes should be measured in finished ciders, rather than juice to accurately evaluate effects of the processing steps on quality.

Impact of apple cultivar, ripening stage, fermentation type and yeast strain on phenolic composition of apple ciders

Hydroxycinnamic acids and flavonoids in apple juices and ciders were studied using liquid chromatography. Samples were produced from four different Estonian apple cultivars using unripe, ripe and overripe apples, and six different commercial yeasts including Saccharomyces cerevisiae, Saccharomyces bayanus, and Torulaspora delbrueckii strains. Part of the samples was additionally inoculated with malolactic bacteria, Oenococcus oeni. The most notable difference among the samples was the appearance of phloretin in malolactic ciders in comparison to conventional ciders and the juices. Furthermore, the apple cultivars were significantly different in their phenolic contents and compositions. Additionally, ciders and juices made from unripe apples contained more phenolic compounds than the ripe or overripe, but the effect was dependent on cultivar. The commercial yeast strains differed in the release of free HCAs, especially p-coumaric acid, during the yeast fermentation. In ciders inoculated with S. bayanus, the content was higher than in ciders fermented with S. cerevisiae.